1. Field of the Invention
The invention is generally related to holding tools for machining parts and more particularly to a tool for rounding and/or holding a cylinder.
2. General Background
It is necessary in a variety of industries to work with a cylinder such as a pipe during machining of the cylinder to meet requirements for use. It is also sometimes necessary for the same holding tool to be used to cause rounding of the cylinder within very close tolerances. Especially for large diameter cylinders such as those used in rocket motors, pressure vessels, or large pipelines, it is difficult to find a tool that is can be set up in a reasonable amount of time, has repeatable accuracy, is reliable, and provides for ease of use without error. Such tools are commonly set up on a rotating table on which the cylinder is placed. There are several known approaches to such tools. One is the use of multiple jaws on the rotating table of the machine being used. Another is an internal thick walled cylinder with spider legs and mechanical adjustments with no centering capability. Another is the use of expansion rings where an internal rotating ring connected to shoes with rigid links causes expansion of shoes to a given diameter. Another is the use of pipes set across the diameter of the cylinder with threaded rods and nuts such that to move the cylinder radially outward, the nut is tightened against the pipe pushing the threaded rod against the cylinder. This approach is not very accurate and is very time consuming. Another approach has been to put a large, thick cylinder inside the cylinder being rounded and jacking between the two using a variety of jacking devices.
Although the above approaches provide "rounding", none center the part in the process of rounding, and most are labor and time consuming. Most are used in conjunction with chuck jaws attached to the turntable to assist in the rounding and centering process. The issue is that this eliminates the possibility of machining the bottom and the top of the cylinder in the same setup. None of the known devices allows a controlled movement for an infinite multitude of rounding and eccentric configurations of closed looped surfaces within one rounding tool.
For cylinders used in rocket motors, there is a need to round a large cylinder for three applications, one on a vertical boring machine, one on a horizontal boring machine, and the third on a horizontal lathe. In addition to the rounding function, the tool must also act as the chuck that holds the part to allow machining to be performed on the inside diameter and the outside diameter at both ends of the cylinder without requiring a second setup or readjustment of the part. The tool must provide sufficient rigidity or backing to allow machining of the cylinder without allowing the cylinder to deflect or vibrate. The tool must also hold the part on the center of the rotating table at each end of the cylinder.